Process for cleaning tin plate



Aug. 31 ,1926. 1,598,125

. C. FINNEGAN PROCESSFOR CLEANING TI N PLATE Filed Nov. 4, 1925 PatentedAug. 31, 1926.

CHARLES FINNEGAN, 0F GIBSONIA, PENNSYLVANIA.

PROCESS FOR CLEANING TIN PLATE.

Application filed November 4, 1925. Serial No. 66,822.

The invention relates to a process for cleaning tin-plate. In theprocess of manu facture, tin-plate receives an oil treatment tofacilitate the spreading of the tin coating and the removal of anyexcess immediately after it emerges from the bath. It then be comesnecessary to remove the oil, and it has been the practice to accomplishthis by carrying the sheets through a bin or compartment supplied withmiddlings and brushes. The middlings absorb the major portion of theoil, which action is facilitated by the brushes, the final brushesserving to remove the middlings themselves preliminary to the dischargeof the plates from the bin. This procedure cleans the platessufliciently for most purposes, but there still remains a very thin fihnof oil and often some small particles of middlings; and this oil and theparticles of middlings which remain are more or less objectionable whenthe plates are to be decorated or printed, as the quality of the work ismaterially affected by these materials. If the quantity of oil remaininghappens to be excessive, it entirely unfits the plates for printing anddecorating and this sometimesr'esults in their rejection by thepurchaser. The cleaning with the mid dlings also presents objectionablefeatures, among which is the cost and the difficulty of maintaining theapparatus at a uniform degree of eificiency unless a high degree of careis observed.

The. present invention is designed to provide a process for insuringthat the oil is entirely removed from the plates, as well as anyparticles of the middlings left after the brushing operation. It isfurther designed, in one of its embodiments, to do away entirely withthe necessity of cleaning with the middlings and so avoid the expenseand other objections incident to the size of the middlings.

Briefly stated, the desired result is secured by passing the platesslowly through a furnace which removes the oil, apparently by avolatizing or vaporizing action, and drys or carbonizes any middlingparticles, so that they drop away from the plates or are readily blownaway by air blasts as the plates emerge from the furnace. Thetemperature of the furnace is such that the oil is entirely removed, butis below the point where there is danger of injury to the coating bysoftening or crystallizing, sometimes referred to as burning. The platesare in this manner entirely freed from any trace of oil. The plates arepreferably carried through the furnace in an upright position upon anendless conveyor, so that both sides are exposed to the action of theheat and a free vaporizing of the oil from both surfaces occurs duringthe movement through the furnace. A temperature ranging from 250 to 400degrees Fahrenheit is suflicient to secure the desired removal of theoil without danger of injury to the tin coating upon surfaces of theplates, the degree of heat applied depending on the time given for thepassage of the plates through the furnace. The plates are deposited upontrucks, as they emerge from the furnace, in packs of size convenient forhandling, and because of the absence of any oil films on the surfaces,any tendency of the plates to slide laterally in the pack duringhandling is avoided, thus rendering the packs easier to move and packthan is the case with plates having slightly oiled surfaces.

Two forms of apparatus for use in carrying out the process are shown ina diagramm'atic way in the accompanying drawings, wherein:

Figure 1 is a partial side elevation and partial section through oneform of apparatus in which the middlings cleaning bin is employed. Fig.2 is a section on the line IIII of Fig. 1. And Fig. 3 is a partial sideelevation and partial section through a modified form of apparatus inwhich the, middlings cleaning device is dispensed with.

Referring first to the showing of Fig. 1, the numeral 1 designates theend of the tank carrying the tinning bath in the end of which is an oilbath through which the tinned plates are passed to facilitate thedraining off of any excess tin. The plates are then carried between thepairs of driven rolls 2 to the middlings bin 3. This bin is providedwith the usual sets of felt rolls 4, driven at varying speeds tofacilitate the rubbing away to bring a maximum quantity of the middlingsinto contact with the plates. A continuous supply of middlings is passedthrough the bin from the spout 5, such middlings being removed from thebottom of the bin through the outlet 6 and returned to the hopper 7 byany suitable transfer mechanism, not shown. The outlet end of the bin isprovided with the usual driven brush rollers 8 for removing theparticles of of the oil upon the plates and middlings adhering thereto.The middlings cleaning unit is a device well known in the art andconstitutes no part of the present invention.

The heating or vaporizing furnace 9 is arranged in alignment with theoutlet end'of the middlings cleaner. It is of the tunnel type andincludes an endless carrier in the form of a pair of chains 10,10,passing around the pairs of sprockets 11, 12 at the ends of the furnaceand carried upon the shafts 13 and 14. One of these shafts is providedat its end outside the furnace w1th another sprocket 15 (Fig. 2) drivenslowly by suitable operating means not shown, the movement beingpreferably step-by-step to facilitate the reception of the plates fromthe brush rollers 8. Extending between the chains, in U-form, are thewires 16 (Fig. 2) which act as supports for holding the plates 17 inupright position as they pass through the furnace, as indicated inFig. 1. The plates are in this way exposed to the full vaporizing efiectof the heated gases of the furnace, the heat being preferably suppliedfrom the perforated gas burners 18 extending transversely of the furnaceadjacent the bottom wall. Any other suitable heating means may besubstituted for the gas burners. Air blasts from the vertical perforatedheaders 18 (supplied from a pump or compressor) serve to remove anyparticles of middlings which remain adhering to the plates.

In operation, the plates passing through the middlings bin 3 are cleanedfrom the bulk of the oil thereon and are brushed free from the majorportion of the middlings by the brushes 8. The conveyor in the furnace9'may be given a step-by-step movement timed so as to correspond to thefeed of the plates from the bin so that the attention of an operator atthis point may be largely dispensed with. The plates are'heated and theoil films dried away or oxidized as the plates pass through the furnace.and upon their exit may be received and stacked upon a truck such as theone 19 of Fig. 1, the truck being removed, when the ack is complete, andanother truck moved into position.

Fig. 3 illustrates a modification of the apparatus and process, themiddlings bin being omitted in this case, and the plates being carrieddirect to the furnace 9, which is the same in e uipment as the furnaceof Fig. 1, the parts eing similarl numbered. In this case, the pairs ofrol s 20 deliver the plates 21 to the brush rolls 22, which remove thebulk. of the oil, preliminary to feeding the plates into the endlessconveyor.

Any other suitable means may be used in place of the brushes 22 forscraping off or removing the bulk of the oil. The cleaning effect ofthese mechanical rubbing or scraping means is not the same as thatsecured by the middlings bin, but the films of oil must still be removedby the heating action in the furnace.

The invention is not limited to the form of tunnel kiln shown. Variousshapes may be used depending on conditions and the space available,which may not permit of a straight-away kiln, such as the oneillustrated. The showing of the kiln and other apparatus is diagrammaticthroughout, and it will be understood that details such as the number ofrolls or brushes and their spacing may be varied in accordance withpractical requirements in the art. Also that the usual accessories forhandling sheets may be utilized such as suitable automatic means forstacking the plates and squaring up the piles on the trucks. Anadvantage is involved in feeding the plates directly into the ovenwithout stacking them up before the heat treatment, in that, anyparticles of foreign material, such as the middlings, adhering to theplates will drop off more readily during such heat treatment, if suchparticles have not been caused to adhere more firmly by pressure, suchas they would be exposed to in stacking.

What I claim is 1. A process for removing the oil coating applied totin-plate in the process of manufacture which consists in carrying theplates through a chamber exposed to a temperature sufficient to removethe oil, but below a point at which the coating uponthe plates isaffected.

2. A process for removing the oil coating applied to tin-plate in theprocess of manufacture which consists in carryin the plates through achamber in an uprig t position an dexposed to a temperature such as toremove the oil without affecting the metal coating upon the plates.

3. A process for removing the oil coating applied to tin-plate in theprocess of manufacture which consists in carrying the plates through achamber exposed to a temperature suflicient to remove the oil, but belowa point at which the coating upon the plates is affected, and applying ablast of air to the plates after the oil is removed.

4. A process for removing the oil coating applied to tin-plate in theprocess of manufacture which consists in carrying the plates through achamber in an upright position and exposed to a temperature such as toremove the oil without affecting the metal coating upon the plates andapplying .a blast of air across the plates to remove any particles ofmaterial adhering thereto.

5. A process for removing the oil coating applied to tin-plate in theprocess of manufacture which consists in brushing the surfaces of theplates to remove the bulk of the oil and then carrying them through athem, as the move along, shifting the plates chamber exposed to atemperature such as to an uprig t position, and exposing them to dry awathe oil remaining on the plates, 'to a relatively high temperature, asthe but not su cient to affect the metal coating are carried aheadto'remove the film of 011 I upon the plates. adhering thereto, butWithout crystallizing 1 6. A process for removing the oil coating thetin coating.

applied to tin plate in the process of manu- In testimony whereof, Ihave hereunto facture, which consists in carrying the plates subscribedmy name this 3rd day of N ovemahead in series, exposing the plates toconber, 1925.

I n tact with absorbent material and brushing CHARLES FINNEGAN.

